Pulse combustion system for a water heater

ABSTRACT

A water heater. The water heater includes a water circuit adapted to conduct water to be heated, a combustion system operable to produce products of combustion and operable to provide the products of combustion to heat water in the water circuit, and a fuel train assembly configured to provide fuel to the combustion system. The fuel train assembly includes a gas expansion chamber, a first gas shut-off valve positioned upstream of the expansion chamber, and a second gas shut-off valve positioned downstream of the expansion chamber.

BACKGROUND

The present invention relates to water heaters, and more particularly to pulse combustion systems for gas fired water heaters.

SUMMARY

In one embodiment, the invention provides a water heater. The water heater includes a water circuit adapted to conduct water to be heated, a combustion system operable to produce products of combustion and operable to provide the products of combustion to heat water in the water circuit, and a fuel train assembly configured to provide fuel to the combustion system. The fuel train assembly includes a gas expansion chamber, a first gas shut-off valve positioned upstream of the expansion chamber, and a second gas shut-off valve positioned downstream of the expansion chamber.

In another embodiment, the invention provides a fuel delivery system for delivering fuel to a combustion system of a water heater tank assembly. The fuel delivery system includes a gas expansion chamber, a first supply line supplying fuel to the gas expansion chamber, a first gas shut-off valve positioned in the first supply line and upstream of the gas expansion chamber, a second supply line supplying fuel from the gas expansion chamber to the combustion system, and a second gas shut-off valve positioned in the second supply line and downstream of the gas expansion chamber.

In another embodiment, the invention provides a fuel train assembly for providing fuel to a combustion system. The fuel train assembly includes a gas expansion chamber, a first gas shut-off valve positioned upstream of the gas expansion chamber to selectively interrupt flow of fuel into the gas expansion chamber, and a second gas shut-off valve positioned downstream of the gas expansion chamber to selectively interrupt flow of fuel into the combustion system.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a water heater system according to the invention.

FIG. 2 is an exploded view of a tank extension and combustion system of the water heater system.

FIG. 3 is a perspective view of the tank extension and combustion system of the water heater.

FIG. 4 is a schematic of the fuel train assembly for use with the system of FIG. 1.

FIG. 5 is an end view of an inlet air tube coupled to a combustion chamber of the water heater system.

FIG. 6 is another embodiment of an air inlet tube of the present invention.

FIG. 7 is a perspective view of one embodiment of a gas flapper valve for use in the fuel train of FIG. 4.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

The present invention is intended for use with a gas fired water heater. Furthermore, the water heater system and fuel train assembly are described for use with a pulse combustion system that creates pressure pulses. However, the water heater system and fuel train assembly may be utilized with other types of combustion technologies.

FIG. 1 illustrates a water heater system 10 embodying the present invention. The water heater system 10 includes an inlet air vent 14, an inlet air decoupler 18, inlet air piping 22, a blower 26, an air chamber 30, a tank extension 34, a combustion system 36 (FIG. 2), and a generally cylindrical tank 38. The water heater system 10 further includes an exhaust decoupler 42, exhaust piping 46 and a muffler 50. The water heater system 10 further includes a fuel train assembly 54 (illustrated schematically in FIGS. 2, 3, and 4) configured to provide fuel to the combustion system 36 through a fuel nozzle 62 (illustrated schematically in FIGS. 3 and 4).

In general, the pulse combustion system 36 works through ignition of an air/fuel mixture in a combustion chamber 58 of the combustion system 36 to create cyclical pressure pulses in the combustion chamber 58 and the pulse combustion system 36 as a whole. The cyclical pressure pulses result in alternating positive and negative pressure in the combustion chamber 58, thereby allowing additional air and fuel to be drawn into the combustion chamber 58 for subsequent ignitions.

With reference to FIG. 1, the inlet air vent 14 is configured to deliver air from an atmosphere vent to the inlet air decoupler 18 through inlet air piping 22. The inlet air piping 22 is manufactured from PVC piping; although in other embodiments, other suitable materials may be used. The inlet air decoupler 18 is configured to provide acoustic control or disengagement of the inlet air, such that the inlet air piping 22 configuration does not affect the overall acoustic resonance of the combustion system 36. The inlet air decoupler 18 is coupled to the blower 26 with additional inlet air piping 22 configured to deliver the inlet air to the blower 26. The blower 26 operates at an rpm as determined by the system requirements.

As shown in FIG. 2, the generally cylindrical tank 38 has a dome-shaped upper head 66 and is preferably formed of corrosion resistant material, such as glass coated steel. The water tank 38 has a tank wall 70 defining an interior space 74. The water tank 38 is adapted to contain water to be heated. The tank extension 34 includes an extension wall 78, the air chamber 30, and at least a portion of the combustion system 36, which includes the combustion chamber 58 and an exhaust tube arrangement 82. The tank extension 34 includes a flange 86 that is detachably mounted to a flange 90 of the tank wall 70 with fasteners. The extension wall 78 defines an extension space 92 (see FIGS. 2 and 3) that is configured to communicate with and be flooded with water from the interior space 74 of the water tank 38. The tank extension 34 further defines an extension axis 94. The extension axis 94 extends along a longitudinal length of the tank extension 34.

The tank extension 34 provides additional space to accommodate the combustion chamber 58 and at least a portion of the exhaust tube arrangement 82. In the illustrated embodiment, the exhaust tube arrangement 82 includes coils of tubes that facilitate heat exchange from the products of combustion to the water surrounding the exhaust tubes 82. The combustion chamber 58 is also submerged in water in the tank extension 34 and provides heat exchange to the surrounding water. Accordingly, the heat exchange capacity of the water heater is greater than the heat exchange capacity of a water heater without the flooded tank extension because the flooded tank extension provides for additional space for heat exchange. In further embodiments, the tank extension is extendible to accommodate additional exhaust tubes for increased heat exchange with the water surrounding the exhaust tubes. The tank extension 34 can extend from other areas of the water tank as long as the water heater 10 and combustion system 36 can still effectively and efficiently operate. The tank extension 34 may include a wall 96 (FIG. 3) at flange 44 separating the exhaust decoupler 42 from the extension space 92 to prevent flooding of the exhaust decoupler 42.

With additional reference to FIGS. 2 and 3, the air chamber 30 is partially disposed in the extension space 92 and extends through the extension wall 78 in a direction substantially perpendicular to the extension axis 94 of the tank extension 34. The air chamber 30 may extend through the extension wall 78 at any radial angle, and preferably extends substantially perpendicular to the extension axis 94 of the tank extension 34 to minimize the portion of the air chamber 30 within the extension space 92. Extending the air chamber 30 through the extension wall 78 provides more space in the extension space 92 for exhaust tubes 82 when compared to containing the entire air chamber 30 within the tank extension 34. This may provide more space for additional tubes 82 and heat exchange surfaces. The air chamber 30 includes an upper chamber or decoupler 98, and a lower chamber 102. The decoupler 98 receives air from the blower 26 and decouples the air from pressure pulses created during operation of the pulse combustion system 36. An air inlet tube 106 having a smaller diameter than the diameter of the air decoupler 98 extends through the air chamber 30 and is coupled to the combustion system 36 to limit the amount of air delivered to the combustion system 36. The air inlet tube 106 is configured as an aerodynamic valve that prevents pulsations created by the combustion process from being relieved in a reverse direction through the air inlet tube 106 and also provides a conduit for air to enter the combustion system 36.

FIGS. 5 and 6 illustrate configurations for air inlet tube 106A, 106B which provide additional pressure drop during the positive pressure cycle of the combustion process. FIG. 5 shows the air inlet tube 106A divided into smaller passages by way of a plurality of smaller air tubes 110 a, 110 b, 110 c, 110 d, 110 e, 110 f, 110 g positioned within the air inlet tube 106A that are configured to collectively cause additional pressure drop to counteract increased gas velocity created by the detonation and expansion of fuel in the combustion chamber 58. The air tubes may extend the full length or a partial length of the air inlet tube. The additional pressure drop during the expansion phase may improve combustion quality and reduce noise from the inlet air side of the system. FIG. 6 shows another embodiment of the air inlet tube 106B having a series of concentric or nested tubes 110 h, 110 i, 110 j of increasingly smaller diameter that are configured to collectively cause additional pressure drop within the air inlet tube 106B.

As shown in FIG. 3, the combustion chamber 58 of the combustion system 36 is at least partially disposed in the extension space 92 and in fluid communication with the air chamber 30 to receive air from the air inlet tube 106. The combustion chamber 58 is configured to receive air and fuel for combustion. The water heater system 10 further includes an igniter tube 114, a flame sensor tube 118, and a fuel delivery tube 120.

The igniter tube 114 and flame sensor tube 118 are adapted to provide access to the combustion system 36 through the extension wall 78 for an igniter and a flame sensor, respectively. The igniter may include a spark igniter, a hot surface igniter, or any other suitable igniter for the type of fuel and combustion system 36 in the water heater 10. The flame sensor is used by a control system of the water heater to monitor the combustion state within the combustion system 36. The fuel delivery tube 120 communicates with the fuel nozzle 62 to facilitate delivery of fuel through the extension wall to the combustion system 36. The fuel delivery tube 120 may be adapted for supplying natural gas, propane gas, or another suitable fuel for the application. The tubes 114, 118, 120 also facilitate service of the igniter, flame sensor, and fuel nozzle by providing access to them from outside the tank extension 34.

Turning now to FIG. 4, the fuel train assembly 54 includes, in addition to the already-mentioned nozzle 62, a regulator 122, a first shut-off valve 126, a gas expansion chamber 130, a gas flapper valve 134, a second shut-off valve 138, and an orifice 142. During normal operation, the fuel flows in a direction 143. The regulator 122 is configured to control the delivery pressure of the fuel as it passes through a first supply line, or piping 146A, to the gas expansion chamber 130. The first gas shut-off valve 126 is a solenoid valve in the illustrated embodiment, although it can take the form of a slow-opening valve or any suitable valve in other embodiments. The first gas shut-off valve 126 is positioned upstream of the gas expansion chamber 130 and is configured to control the flow of fuel to the gas expansion chamber 130. The first gas shut-off valve 126 is operable between a closed position, wherein fuel is not allowed to flow through the valve 126, and an open position, wherein fuel is allowed to flow through the valve 126.

The gas expansion chamber 130 functions as a holding tank for fuel and as a plenum chamber, thereby providing a dampening effect on pulsations caused by feedback from the rapid expansion and contraction of fuel in the combustion chamber 58 during the pulse combustion operation. The combustion system 36 may experience a pressure change of 1 psi during the pressure pulses. The expansion chamber 130 retains fuel during standby to enable fuel flow upon ignition without delay or interruption. Fuel is delivered out of the gas expansion chamber 130 and through the remainder of the fuel train assembly 54 as dictated by the demands of the pulse combustion system 36. The dampening effect of the expansion gas chamber 130 prevents any unintended pressure changes upstream of the gas expansion chamber 130 in the upstream direction resulting from feedback from the pulse combustion and also prevents the products of combustion from traveling upstream of the gas expansion chamber 130.

The gas flapper valve 134 is a one-way valve configured for flow of fuel in a downstream direction. The gas flapper valve 134 is configured to open and close based on the pressure changes created in the combustion system 36 during the pulse combustion process. In operation, rapid expansion of the fuel during ignition in the combustion chamber 58 creates increased pressure in the fuel train assembly 54. The increased pressure closes the gas flapper valve 134. The closed gas flapper valve 134 minimizes pressure pulses from entering the expansion chamber 130 through the gas flapper valve 134. As combustion consumes the fuel, the pressure decreases, thereby allowing the gas flapper valve 134 to open. The open gas flapper valve 134 allows fuel to flow from the gas expansion chamber 130 through the remaining portion of the fuel train assembly 54 to facilitate the combustion.

The fuel train assembly 54 may use a single gas flapper valve. However, in other embodiments and as shown in FIG. 7, multiples of a single gas flapper valve 134 can be used in a gas flapper holder 148 to achieve a variety of inputs as required by the particular application. The gas flapper valve is configured for inputs up to approximately 350,000 BTUH. For example, for inputs less than 300,000 BTUH, one gas flapper valve and expansion chamber are used. However, for inputs between 300,000 and 700,000 BTUH, two flapper valves are used with the expansion chamber. In other embodiments, more than two flapper valves may be used for inputs greater than 700,000 BTUH. The number of gas flapper valves can be adjusted according to the input required by the particular water heater system application. Apertures 149 integrally formed in the holder 148 are configured to receive flapper valves 134. The apertures 149 are blocked off if not in receipt of a flapper valve 134. Similarly, the gas expansion chamber is designed to accept a number of gas flapper valves depending on the desired throughput of the application.

The second gas shut-off valve 138 is a solenoid valve; however, in other embodiments, the second gas shut-off valve may be a slow-opening valve or any suitable valve. The second gas shut-off valve 138 is positioned downstream of both the gas expansion chamber 130 and the gas flapper valve 134 and configured to minimize gas leakage through the second supply line, or piping 146B, when the pulse combustion system 36 is in standby or not in operation. In other embodiments, the second gas shut-off valve 138 may be positioned downstream of the gas expansion chamber 130 and upstream of the gas flapper valve 134. The second gas shut-off valve 138 is also configured to maintain the fuel in the piping 146B during standby, such that when the system is operational, the fuel is already pressurized in the piping 146B and prepared for delivery to the combustion system 36. Accordingly, the second gas shut-off valve 138 improves ignition because the second shut-off valve 138 maintains the pressurized fuel in piping 146B during standby. The first and second shut-off valves 126, 138 are closed during standby to prevent gas from leaking into the combustion system 36 when the system is not in operation. Such leakage into the combustion system 36 when the system is not in operation could result in leakage of fuel out of the blower 26 or through the exhaust venting system. The fuel train assembly 54 further includes the orifice 142 configured to restrict the flow of fuel before the fuel is delivered to the fuel nozzle 62, such that the orifice 142 provides a further control on the flow rate of fuel through the fuel nozzle 62 to the combustion chamber 58 of the combustion system 36.

Each of the exhaust tubes 82 is configured to receive the products of combustion. The exhaust tubes 82 extend into the interior space 74 of the water tank 38. The exhaust tubes 82 are bundled in pairs to provide efficient heat exchange in the condensed space of the water tank 38.

Each of the exhaust tubes 82 communicates at a first end 150 with a combustion manifold 154 and at a second, opposite end 158 with an exhaust manifold 162. The combustion manifold 154 extends into the interior space 74 of the water tank 38 and is configured to receive and distribute the products of combustion to each of the exhaust tubes 82. The exhaust manifold 162 receives products of combustion from each of the exhaust tubes 82 and delivers the products of combustion to the exhaust decoupler 42. The exhaust manifold 162 extends through the wall 96 (see FIG. 3), but is sealed with respect to the wall so that water in the extension space 92 cannot flow into the exhaust decoupler 42.

The exhaust decoupler 42 receives the products of combustion and expands the products of combustion to reduce pressure and decouple the products of combustion from the pressure pulses arising from pulse combustion. An exhaust gas outlet 166 extends from the exhaust decoupler 42 and provides an outlet for exhaust gas, while the condensate drains from a drain aperture 168 separate from the exhaust gas outlet 166. The muffler 50 is coupled to the exhaust gas outlet 166 with exhaust piping 46. The muffler 50 is configured to reduce noise produced within the system. Additional exhaust piping 46 connects the muffler 50 to an external vent configured to release the exhaust gas external of the water heater system 10.

In operation, an electronic control provides an ignition sequence, water temperature control, and safety system. A sensed drop in water temperature initiates the ignition sequence, which begins with activation of the blower 26 to purge the combustion system 36. The blower 26 then decreases in rpm and the ignition system activates. The blower rpm is lowered because a lower rpm from the blower 26 may improve ignition. The ignition system is activated prior to opening of the gas shut-off valves 126, 138 and subsequent delivery of fuel to the combustion system 36. Once the gas shut-off valves 126, 138 are opened, fuel enters the combustion chamber 58 and is ignited by the igniter. Once this process is started, the pulsating combustion is sustained as a result of the acoustic resonance of the combustion system 36 as a whole. The flame sensor monitors the existence of the flame throughout combustion. Following ignition, the blower rpm may be increased, and the blower 26 remains operational throughout combustion. The electronic control substantially simultaneously adjusts the first and second gas shut-off valves 126, 138 between an open position, in which fuel flows through both valves, and a closed position, in which fuel does not flow through either valve, based on the demands of the system 10.

Air is delivered by the air chamber 30 and air inlet tube 106 to the combustion chamber 58 of the combustion system 36 where the air is mixed with fuel provided by the fuel train assembly 54. Following ignition of the air/fuel mixture, the products of combustion enter the combustion manifold 154. The combustion manifold 154 distributes the products of combustion to each of the exhaust tubes 82. The products of combustion proceed down each of the exhaust tubes 82. Preferably, as much energy in the form of heat as possible is transferred from the products of combustion to the water in the tank 38, even to the point of permitting condensation of the products of combustion. Any condensate drainage flows toward the exhaust manifold 162. The exhaust manifold 162 delivers the exhaust gas and condensate drainage to the exhaust decoupler 42. The exhaust gas exits the water heater 10 through the exhaust gas outlet 166 and continues through the muffler 50 to the external vent. The condensate drainage exits the exhaust decoupler 42 through a drain aperture 168 separate from the exhaust gas outlet 166.

The system is configured to be scaleable in size for basic input ranges from 140,000 to 2.5 million BTUH. In other embodiments, the system may be configured to be scaleable in size for basic input ranges less than 140,000 BTUH or greater than 2.5 million BTUH. Manifold tube lengths, tube diameters, and exhaust tube lengths are selected for the particular application of the water heater system and to maintain acoustic resonance of the combustion system 36 as a whole.

In the pulse combustion system 36, the length of tubing provides the desired acoustic resonance required for satisfactory operation. For instance, the length and diameter of the inlet air piping 22 is adjustable between the inlet air decoupler 18 and the blower 26. Such adjustment of the length and diameter of the inlet air piping 22 provides an additional tuning method for the pulse combustion system 36 to obtain a desired resonance. Tuning can also be accomplished by providing or adjusting the length and diameter of tubing between the blower 26 and the air decoupler 98 or by adjusting the manifold tube lengths, tube diameters, or exhaust tube lengths.

The length of the air chamber 30 and the size of the air decoupler 98 are determined by the requirements of the pulse combustion system 36 and water heater 10 application. Furthermore, the tank extension 34 and components of the fuel train assembly 54 and the combustion system 36 can be of various sizes to accommodate different heating capacities and applications.

Various features and advantages of the invention are set forth in the following claims. 

1. A water heater comprising: a water circuit adapted to conduct water to be heated; a combustion system operable to produce products of combustion and operable to provide the products of combustion to heat water in the water circuit; and a fuel train assembly configured to provide fuel to the combustion system, the fuel train assembly comprising: a gas expansion chamber; a first gas shut-off valve positioned upstream of the expansion chamber; and a second gas shut-off valve positioned downstream of the expansion chamber.
 2. The water heater of claim 1 wherein the combustion system is a pulse combustion system creating pressure pulses.
 3. The water heater of claim 1 wherein the first gas shut-off valve and second gas shut-off valve substantially simultaneously adjust between an open position, in which fuel flows through both valves, and a closed position, in which fuel does not flow through either valve.
 4. The water heater of claim 1, the fuel train assembly further comprising a gas flapper valve positioned downstream of the gas expansion chamber and configured to permit substantially one-way flow of fuel in a downstream direction.
 5. The water heater of claim 1, the fuel train assembly further comprising a first supply line positioned upstream of the gas expansion chamber and supplying fuel to the gas expansion chamber and a second supply line supplying fuel from the gas expansion chamber to the combustion system.
 6. The water heater of claim 1, the fuel train assembly further comprising a regulator positioned upstream of the gas expansion chamber to control delivery pressure of fuel to the gas expansion chamber.
 7. A fuel delivery system for delivering fuel to a combustion system of a water heater tank assembly, the fuel delivery system comprising: a gas expansion chamber; a first supply line supplying fuel to the gas expansion chamber; a first gas shut-off valve positioned in the first supply line and upstream of the gas expansion chamber; a second supply line supplying fuel from the gas expansion chamber to the combustion system; and a second gas shut-off valve positioned in the second supply line and downstream of the gas expansion chamber.
 8. The fuel delivery system of claim 7 wherein the combustion system is a pulse combustion system creating pressure pulses.
 9. The fuel delivery system of claim 7, further comprising a gas flapper valve positioned in the second supply line downstream of the gas expansion chamber.
 10. The fuel delivery system of claim 7 wherein the first gas shut-off valve and second gas shut-off valve substantially simultaneously adjust between an open position, in which fuel flows through both valves, and a closed position, in which fuel does not flow through either valve.
 11. The fuel delivery system of claim 7, further comprising a regulator positioned in the first supply line upstream of the gas expansion chamber.
 12. A fuel train assembly for providing fuel to a combustion system, the fuel train assembly comprising: a gas expansion chamber; a first gas shut-off valve positioned upstream of the gas expansion chamber to selectively interrupt flow of fuel into the gas expansion chamber; and a second gas shut-off valve positioned downstream of the gas expansion chamber to selectively interrupt flow of fuel into the combustion system.
 13. The fuel train assembly of claim 12 wherein the first gas shut-off valve and second gas shut-off valve substantially simultaneously adjust between an open position, in which fuel flows through both valves, and a closed position in which fuel does not flow through either valve.
 14. The fuel train assembly of claim 12, further comprising a gas flapper valve positioned downstream of the gas expansion chamber and configured to permit substantially one-way flow of fuel in a downstream direction.
 15. The fuel train assembly of claim 12 wherein the combustion system is a pulse combustion system creating pressure pulses.
 16. The fuel train assembly of claim 12, further comprising a first supply line supplying fuel to the gas expansion chamber and a second supply line supplying fuel from the gas expansion chamber to the combustion system.
 17. The fuel train assembly of claim 12, further comprising a regulator positioned upstream of the gas expansion chamber and configured to control delivery pressure of fuel to the gas expansion chamber. 